Pneumatic tire

Abstract

To provide a pneumatic tire that can be improved in running performance on an ice / snow road, while securing steering stability.SOLUTION: In a pneumatic tire according to the present invention, a plurality of inner intermediate blocks 18C formed in parallel in a tire circumferential direction CD and a plurality of inner intermediate slits 16C formed between the inner intermediate blocks 18C1 and 18C2 are arranged in an inner intermediate region 14C partitioned by an inner center main groove 12B and an inner shoulder main groove 12D. The plurality of inner intermediate blocks 18C1 and 18C2 comprise first inner intermediate blocks 18C1 in which first inner intermediate notches 40 opened to the inner center main groove 12B are formed and second inner intermediate blocks 18C2 in which second inner intermediate notches 41 opened to the inner shoulder main groove 12D are formed. The first inner intermediate blocks 18C1 and the second inner intermediate blocks 18C2 are arranged alternately in the tire circumferential direction CD.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Some pneumatic tires are known to have sipes in blocks formed by main grooves extending in the circumferential direction of the tire or slits extending in the axial direction of the tire (for example, Patent Documents 1 and 2 below). In such pneumatic tires, the provision of a large number of grooves and sipes enhances the drainage effect, edge effect, and water absorption effect, improving driving performance on icy and snowy roads, but reduces the rigidity of the blocks, which tends to reduce steering stability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-105615 A [Patent Document 2] JP 2013-71647 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a pneumatic tire that can improve driving performance on icy and snowy roads while ensuring steering stability. [Means for solving the problem]

[0005] The present invention includes the embodiments set forth below.

[0006] [1] A pneumatic tire having a tread with three or more main grooves extending in the tire circumferential direction formed in the tread rubber, and a mounting direction on a vehicle is specified, The tread rubber of the pneumatic tire includes an outer center main groove provided on the vehicle outer side of the tire equatorial plane, an inner center main groove provided on the vehicle inner side of the tire equatorial plane, an inner shoulder main groove adjacent to the inner center main groove on the tire axially outer side, and an inner middle region defined by the inner center main groove and the inner shoulder main groove, The inner intermediate region includes a plurality of inner intermediate blocks arranged in a tire circumferential direction and a plurality of inner intermediate slits provided between the inner intermediate blocks, the plurality of inner intermediate blocks include a first inner intermediate block having a first inner intermediate notch that opens into the inner center main groove and a second inner intermediate block having a second inner intermediate notch that opens into the inner shoulder main groove, The first inner intermediate blocks and the second inner intermediate blocks are provided alternately in the tire circumferential direction.

[0007] [2] The first inner intermediate block and the second inner intermediate block each have a wave-shaped inner intermediate sipe extending in a direction intersecting the tire circumferential direction so that one end opens into the inner center main groove and the other end opens into the inner shoulder main groove, The amplitude center line of the inner intermediate sipe is bent in opposite directions at a first bend portion provided on the axially inner side of the inner intermediate block and a second bend portion provided on the axially outer side of the inner intermediate block, The pneumatic tire according to [1] above, wherein the inner intermediate sipe is interrupted at one of the first bend portion and the second bend portion.

[0008] [3] The pneumatic tire described in [2] above, wherein the inner intermediate sipes provided in the first inner intermediate block are separated at the second bend portion, and the inner intermediate sipes provided in the second inner intermediate block are separated at the first bend portion.

[0009] [4] The pneumatic tire according to any one of [1] to [3] above, wherein the inner intermediate slit has a first slit bending portion bending from one side in the tire circumferential direction to the other side, and a second slit bending portion bending from the other side in the tire circumferential direction to one side. Effect of the Invention

[0010] By providing the above-mentioned features, the present invention can improve driving performance on icy and snowy roads while ensuring steering stability. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a development view showing the tread pattern of the pneumatic tire of FIG. 1. [Diagram 3] FIG. 3 is an enlarged plan view of a main portion of the tread pattern of FIG. 2. [Figure 4] FIG. 2 is an enlarged plan view of a main portion of a tread pattern showing a center region in an enlarged manner. [Diagram 5] FIG. 4 is an enlarged plan view of a main portion of a tread pattern showing an outer middle region in an enlarged manner. [Figure 6] FIG. 4 is an enlarged plan view of a main portion of a tread pattern showing an inner middle region in an enlarged manner. [Figure 7] Cross-sectional view taken along line AA in Figure 2. [Figure 8] Cross-sectional view of line BB in Figure 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to an embodiment of the present invention will now be described with reference to the drawings.

[0013] In this specification, the ground contact state refers to a state in which a pneumatic tire is mounted on a regular rim, inflated to a regular internal pressure, placed vertically on a flat road surface, and a regular load is applied. The ground contact ends Ei and Eo refer to the axial ends of the tread surface that contacts the road surface in the ground contact state. The sipe refers to a groove whose opening to the ground contact surface is closed in the ground contact state, for example, a narrow groove with a width of less than 2 mm. The main grooves and slits extending in the circumferential direction are grooves that are wider than the sipes and whose opening to the ground contact surface is not closed in the ground contact state, for example, a groove with a width of 2 mm or more.

[0014] A genuine rim is a rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, a genuine rim is a "standard rim" in the JATMA standard, a "Design Rim" in the TRA standard, or a "Measuring Rim" in the ETRTO standard.

[0015] The normal internal pressure is the air pressure that is set for each tire by the standard system that includes the standard on which the tire is based. For example, the normal internal pressure is the "maximum air pressure" in the JATMA standard, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard.

[0016] The normal load is the load that each standard specifies for each tire in the standard system that includes the standard on which the tire is based. For example, the normal load is the "maximum load capacity" in the JATMA standard, the maximum value of the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "LOAD CAPACITY" in the ETRTO standard.

[0017] In the drawings, the symbol CL indicates the tire equatorial plane corresponding to the tire axial center. The symbol AD ​​indicates the tire axial direction (also referred to as the tire width direction). The axially inner side ADi of the tire refers to the direction approaching the tire equatorial plane CL, and the axially outer side ADo of the tire refers to the direction away from the tire equatorial plane CL. The symbol CD indicates the tire circumferential direction, which is a circumferential direction centered on the tire rotation axis. The radially inner side RDi of the tire refers to the direction approaching the tire rotation axis, and the radially outer side RDo of the tire refers to the direction away from the tire rotation axis.

[0018] (1) Cross-sectional structure of pneumatic tire 1 A pneumatic tire 1 according to one embodiment shown in FIG. 1 includes a pair of left and right beads 2, a pair of left and right sidewalls 4 extending radially outward from the beads 2, and a tread 3 connecting radially outer ends of the sidewalls 4 to form a contact surface 8a.

[0019] This pneumatic tire 1 is a tire for which the mounting orientation on a vehicle is specified. That is, the surface to be mounted on the inside of the vehicle and the surface to be mounted on the outside of the vehicle are predetermined. For this reason, for example, a sidewall surface of the tire is provided with a marking for specifying the mounting orientation on the vehicle. In Fig. 1 and Fig. 2, the left side of the tire equatorial plane CL indicated by the symbol OUT is disposed on the outside of the vehicle in the vehicle mounting posture, and the right side of the tire equatorial plane CL indicated by the symbol IN is disposed on the inside of the vehicle in the vehicle mounting posture.

[0020] A ring-shaped bead core 2a is embedded in each of the pair of beads 2. A bead filler 2b made of hard rubber and tapered toward the tire radial outside RDo is provided on the tire radial outside RDo of the bead core 2a.

[0021] The pneumatic tire includes a carcass layer 5 that extends in a toroidal shape across a pair of beads 2. The carcass layer 5 extends from the tread 3 through both sidewalls 4 to the bead 2, and is folded back around the bead core 2a in the bead 2 from the axially inner side ADi to the axially outer side ADo, thereby anchoring both ends of the carcass layer 5.

[0022] The carcass layer 5 is made up of at least one carcass ply. In this example, the carcass layer 5 is made up of one carcass ply, but the carcass layer may be made up of two or more carcass plies.

[0023] The carcass ply constituting the carcass layer 5 is a rubber member in which carcass cords made of organic fiber cords arranged substantially perpendicular to the tire circumferential direction CD are covered with rubber. A sheet-shaped inner liner 6 made of rubber with low air permeability is attached to the inside of the carcass layer 5.

[0024] The tread 3 includes a belt layer 7 provided on the outer peripheral side of the carcass layer 5, a tread rubber 8 having a contact surface 8a that comes into contact with the road surface, and a belt reinforcing layer 9 provided between the belt layer 7 and the tread rubber 8.

[0025] The belt layer 7 is made of at least two cross belt plies in which the belt cords are arranged at an inclination angle of 23° to 29° with respect to the tire circumferential direction CD. In this example, the belt layer 7 has a two-layer structure of a first belt ply 7A arranged on the inner side in the tire radial direction and a second belt ply 7B arranged on the outer peripheral side thereof. Of these, the first belt ply 7A is the widest belt ply. The outer end of the first belt ply 7A in the tire axial direction corresponds to the belt end 7C, which is the end of the belt layer 7 in the tire axial direction.

[0026] As shown in FIG. 2, the surface of the tread rubber 8 is provided with three or more (four in this embodiment) main grooves 12A, 12B, 12C, and 12D extending in the tire circumferential direction CD, and slits 16A1, 16A2, 16B1, 16B2, 16C, 16D, and 16E extending in the tire axial direction AD, forming a tread pattern.

[0027] The belt reinforcing layer 9 is composed of a cap ply having reinforcing cords such as organic fiber cords extending substantially parallel to the tire circumferential direction CD. In this embodiment, as shown in Fig. 1, the belt reinforcing layer 9 is provided in at least a part of the shoulder regions 14D, 14E so as to cover the tire axially outer side ADo of the belt layer 7 from the tire radially outer side RDo, but is not provided in the center region 14A and the intermediate regions 14B, 14C.

[0028] (2) Tread pattern configuration As shown in Figures 1 and 2, the surface of the tread rubber 8 is provided with main grooves extending in the tire circumferential direction CD, including an outer center main groove 12A provided on the vehicle outer side OUT of the tire equatorial plane CL, an inner center main groove 12B provided on the vehicle inner side IN of the tire equatorial plane CL, an outer shoulder main groove 12C adjacent to the outer center main groove 12A on the axially outer side ADo of the tire, and an inner shoulder main groove 12D adjacent to the inner center main groove 12B on the axially outer side ADo of the tire.

[0029] The inner center main groove 12B extends in a substantially straight line in the tire circumferential direction CD. The outer center main groove 12A, the outer shoulder main groove 12C, and the inner shoulder main groove 12D extend in the tire circumferential direction CD in a zigzag manner while bending in the tire axial direction AD. The outer center main groove 12A is narrower and shallower than the other main grooves (the inner center main groove 12B, the outer shoulder main groove 12C, and the inner shoulder main groove 12D).

[0030] For example, the groove widths of the outer center main groove 12A, the inner center main groove 12B, the outer shoulder main groove 12C, and the inner shoulder main groove 12D are preferably 1.5 mm to 4.5 mm, 3.5 mm to 7.5 mm, 4.5 mm to 8.0 mm, and 4.0 mm to 7.5 mm, and more preferably 2.0 mm to 3.9 mm, 3.8 mm to 7.2 mm, 4.7 mm to 7.5 mm, and 4.5 mm to 6.8 mm, respectively. The groove depths of the outer center main groove 12A, the inner center main groove 12B, the outer shoulder main groove 12C and the inner shoulder main groove 12D are preferably 6.0 mm to 7.5 mm, 8.0 mm to 9.5 mm, 8.0 mm to 9.5 mm, and 8.0 mm to 9.5 mm, and more preferably 6.2 mm to 7.2 mm, 8.2 mm to 9.2 mm, 8.2 mm to 9.2 mm, and 8.2 mm to 9.2 mm, respectively.

[0031] The ratio of the groove width of the outer center main groove 12A to the groove width of the inner center main groove 12B is preferably 0.45 to 0.60, and more preferably 0.50 to 0.55. The ratio of the groove depth of the outer center main groove 12A to the groove depth of the inner center main groove 12B is preferably 0.70 to 0.85, and more preferably 0.75 to 0.80.

[0032] The ratio of the groove width of the outer center main groove 12A to the groove width of the outer shoulder main groove 12C is preferably 0.35 to 0.65, and more preferably 0.40 to 0.60. The ratio of the groove depth of the outer center main groove 12A to the groove depth of the outer shoulder main groove 12C is preferably 0.70 to 0.85, and more preferably 0.75 to 0.80.

[0033] The ratio of the groove width of the outer center main groove 12A to the groove width of the inner shoulder main groove 12D is preferably 0.35 to 0.65, and more preferably 0.40 to 0.60. The ratio of the groove depth of the outer center main groove 12A to the groove depth of the inner shoulder main groove 12D is preferably 0.70 to 0.85, and more preferably 0.75 to 0.80.

[0034] A center region 14A is provided between the outer center main groove 12A and the inner center main groove 12B, an outer intermediate region 14B is provided between the outer center main groove 12A and the outer shoulder main groove 12C, and an inner intermediate region 14C is provided between the inner center main groove 12B and the inner shoulder main groove 12D.

[0035] In addition, an outer shoulder region 14D is provided axially outward of the outer shoulder main groove 12C (i.e., between the outer shoulder main groove 12C and the ground contact edge Eo on the outer side of the vehicle), and an inner shoulder region 14E is provided axially outward of the inner shoulder main groove 12D (i.e., between the inner shoulder main groove 12D and the ground contact edge Ei on the inner side of the vehicle).

[0036] (3) Center area 14A As shown in Figures 2 to 4, the center region 14A located between the outer center main groove 12A and the inner center main groove 12B includes a center rib 18A continuing in the tire circumferential direction CD, and a plurality of first center slits 16A1 and a plurality of second center slits 16A2 extending in a direction intersecting the tire circumferential direction CD.

[0037] The first center slit 16A1 is a groove that extends in a direction intersecting the tire circumferential direction CD with one end opening into the outer center main groove 12A and the other end terminating within the center rib 18A. A center notch 16A3 that is triangular in plan view and consists of a recess that is shallower than the first center slit 16A1 is provided on the other end side (the inner center main groove 12B side) of the first center slit 16A1.

[0038] The second center slit 16A2 is a groove that extends in a direction intersecting the tire circumferential direction CD with one end opening into the inner center main groove 12B and the other end terminating within the center rib 18A. In this embodiment, the second center slit 16A2 is shallower than the first center slit 16A1 (see FIG. 7) and is configured as a groove that extends in a direction parallel to the first center slit 16A1. The first center slit 16A1 and the second center slit 16A2 are alternately provided in the center rib 18A in the tire circumferential direction CD.

[0039] Further, the center rib 18A is provided with a plurality of compound sipes 30 arranged in the tire circumferential direction CD, each compound sipe 30 being made up of a central sipe 31 provided in the center in the tire axial direction AD and a pair of left and right end sipes 32 provided on both sides in the tire axial direction AD of the central sipe 31. In this embodiment, the compound sipes 30 are arranged in parallel to each other at intervals in the tire circumferential direction CD.

[0040] The groove width of the first center slit 16A1 and the second center slit 16A2 is preferably 3.0 mm to 6.0 mm, and more preferably 3.3 mm to 5.4 mm.The groove depth of the first center slit 16A1 and the second center slit 16A2 is preferably 4.0 mm to 8.5 mm, and more preferably 4.4 mm to 8.2 mm. The maximum width of the center notch 16A3 (the length of the portion connected to the first center slit 16A1) is preferably 2.0 mm to 5.0 mm, and more preferably 2.3 mm to 4.5 mm. The depth of the center notch 16A3 is preferably 1.0 mm to 5.5 mm, and more preferably 1.3 mm to 5.2 mm. The groove width of the central sipes 31 and the end sipes 32 is preferably 0.15 mm to 1.0 mm, and more preferably 0.3 mm to 0.6 mm. The groove depth of the central sipes 31 and the end sipes 32 is preferably 3.5 mm to 7.0 mm, and more preferably 4.0 mm to 6.5 mm.

[0041] (4) Outer intermediate area 14B As shown in Figures 2, 3 and 5, the outer intermediate region 14B provided between the outer center main groove 12A and the outer shoulder main groove 12C has a plurality of outer intermediate blocks 18B arranged in the tire circumferential direction CD, and a plurality of outer intermediate slits 16B1, 16B2 provided between the outer intermediate blocks 18B.

[0042] The outer intermediate region 14B includes a plurality of first outer intermediate slits 16B1 provided on an extension of the first center slit 16A1 and a plurality of second outer intermediate slits 16B2 provided on an extension of the second center slit 16A2. The first outer intermediate slits 16B1 and the second outer intermediate slits 16B2 are recessed grooves extending in a direction intersecting the tire circumferential direction CD so as to open into the outer center main groove 12A and the outer shoulder main groove 12C, and are provided alternately in the tire circumferential direction CD.

[0043] Specifically, the first outer intermediate slit 16B1 is provided such that at least a part of the opening that opens to the outer center main groove 12A faces the opening of the first center slit 16A1 to the outer center main groove 12A in the extension direction of the first center slit 16A1. The first outer intermediate slit 16B1 forms a continuous groove connected to the first center slit 16A1.

[0044] 3 and 5, the first outer intermediate slit 16B1 has a bent portion 16B1a at the center of the outer intermediate block 18B in the tire axial direction AD. The first outer intermediate slit 16B1 extends in a direction parallel to the first center slit 16A1 on the outer center main groove 12A side from the bent portion 16B1a, and the outer shoulder main groove 12C side from the bent portion 16B1a is inclined in the opposite direction to the first center slit 16A1 with respect to the tire axial direction AD.

[0045] The first outer intermediate slit 16B1 has a groove depth on the outer shoulder main groove 12C side from the bend 16B1a that is shallower than the groove depth on the outer center main groove 12A side from the bend 16B1a and the groove depth of the second outer intermediate slit 16B2.

[0046] In this embodiment, the groove depth of the first outer intermediate slit 16B1 on the outer shoulder main groove 12C side from the bent portion 16B1a is set to the same depth as the groove depth of the second center slit 16A2. The groove depth of the first outer intermediate slit 16B1 on the outer center main groove 12A side from the bent portion 16B1a is set to the same depth as the groove depth of the first center slit 16A1 and the second outer intermediate slit 16B2.

[0047] The second outer intermediate slit 16B2 is not connected to the second center slit 16A2, but is provided such that at least a portion of the opening that opens to the outer center main groove 12A is on an extension line of the second center slit 16A2.

[0048] The second outer intermediate slit 16B2 has a bent portion 16B2a at a position overlapping with the bent portion 16B1a of the first outer intermediate slit 16B1 in the tire axial direction AD. The second outer intermediate slit 16B2 extends in a direction parallel to the second center slit 16A2 on the outer center main groove 12A side from the bent portion 16B2a, and inclines in the opposite direction to the second center slit 16A2 on the outer shoulder main groove 12C side from the bent portion 16B2a with respect to the tire axial direction AD. In this embodiment, the second outer intermediate slit 16B2 is configured as a recessed groove extending in a direction parallel to the first outer intermediate slit 16B1.

[0049] The second outer intermediate block 18B has a first outer intermediate notch 33 at the center in the tire circumferential direction CD of the sidewall facing the outer center main groove 12A, and a second outer intermediate notch 34 at the center in the tire circumferential direction CD of the sidewall facing the outer shoulder main groove 12C. The outer intermediate notches 33, 34 are recesses cut out from the block top surface toward the groove bottoms of the main grooves 12A, 12C to the block bottom, and have a triangular shape in plan view that tapers toward the axial center of the outer intermediate block 18B (away from the sidewall of the block).

[0050] In addition, a first outer intermediate sipe 35 and a second outer intermediate sipe 36 are provided in the center of the outer intermediate block 18B in the tire circumferential direction CD, and third outer intermediate sipes 37, 37 are provided outboard of the first outer intermediate sipe 35 and the second outer intermediate sipe 36 in the tire circumferential direction CD.

[0051] The first outer intermediate sipe 35 is a sipe that extends in a direction intersecting the tire circumferential direction CD with one end connected to the first outer intermediate notch 33 and opening into the outer center main groove via the first outer intermediate notch 33, and the other end terminating in the outer intermediate block 18B. The second outer intermediate sipe 36 is a sipe that extends in a direction intersecting the tire circumferential direction CD with one end connected to the second outer intermediate notch 34 and opening into the outer shoulder main groove 12C via the second outer intermediate notch 34, and the other end terminating in the outer intermediate block 18B.

[0052] The third outer intermediate sipes 37 are provided on the outer side in the tire circumferential direction CD of the outer intermediate block 18B than the first outer intermediate sipe 35, and on the outer side in the tire circumferential direction CD of the outer intermediate block 18B than the second outer intermediate sipe 36. In other words, the outer intermediate block 18B has the first outer intermediate sipe 35 and the second outer intermediate sipe 36 provided between a pair of third outer intermediate sipes 37 spaced apart in the tire circumferential direction CD.

[0053] The third outer intermediate sipe 37 has one end opening into the outer center main groove 12A and the other end opening into the outer shoulder main groove 12C, and is a sipe provided so as to penetrate the outer intermediate block 18B in the tire axial direction AD.

[0054] In this embodiment, the first outer intermediate sipe 35, the second outer intermediate sipe 36, and the third outer intermediate sipe 37 extend in the sipe length direction while repeatedly curving or bending in a plan view, and the cross-sectional shape parallel to the tread surface is a wave shape having an amplitude in the sipe width direction. The amplitude center lines of the first outer intermediate sipe 35, the second outer intermediate sipe 36, and the third outer intermediate sipe 37 are bent at bent portions 35a, 36a, and 37a provided at positions overlapping with the bent portion 16B1a of the first outer intermediate slit 16B1 and the bent portion 16B2a of the second outer intermediate slit 16B2 in the tire axial direction AD, and extend in a direction parallel to the first outer intermediate slit 16B1 and the second outer intermediate slit 16B2.

[0055] The first outer intermediate sipe 35, the second outer intermediate sipe 36, and the third outer intermediate sipe 37 may be sipes extending linearly at the bends 35a, 36a, and 37a as shown in FIG. 4, but the bends 35a, 36a, and 37a may also have a wavy shape having amplitude in the sipe width direction, similar to other portions.

[0056] The groove width of the first outer intermediate slit 16B1 and the second outer intermediate slit 16B2 is preferably 2.5 mm to 5.5 mm, and more preferably 3.0 mm to 5.0 mm. The groove depth of the first outer intermediate slit 16B1 and the second outer intermediate slit 16B2 is preferably 7.0 mm to 8.5 mm, and more preferably 7.2 mm to 8.2 mm.

[0057] The groove width of the first outer intermediate notch 33 and the second outer intermediate notch 34 is preferably 2.5 mm to 5.0 mm, and more preferably 2.8 mm to 4.6 mm. The groove depth of the first outer intermediate notch 33 and the second outer intermediate notch 34 is preferably 1.0 mm to 5.5 mm, and more preferably 1.3 mm to 5.2 mm. The groove width of the first outer intermediate sipe 35, the second outer intermediate sipe 36, and the third outer intermediate sipe 37 is preferably 0.15 mm to 1.0 mm, and more preferably 0.3 mm to 0.4 mm. The groove depth of the first outer intermediate sipe 35, the second outer intermediate sipe 36, and the third outer intermediate sipe 37 is preferably 4.0 mm to 7.0 mm, and more preferably 6.0 mm to 6.5 mm.

[0058] As shown in FIG. 3, assuming that the length W in the tire axial direction from the outer shoulder main groove 12C to the inner center main groove 12B, the length L in the tire circumferential direction CD from the first outer intermediate slit 16B1 to the first outer intermediate slit 16B1 adjacent to one side of the tire circumferential direction CD, the length L1 in the tire circumferential direction CD from the first outer intermediate slit 16B1 to the second outer intermediate slit 16B2 adjacent to one side of the tire circumferential direction CD, and the length L2 in the tire circumferential direction CD from the second outer intermediate slit 16B2 to the first outer intermediate slit 16B1 adjacent to one side of the tire circumferential direction CD, it is preferable that each of the lengths W, L, L1, and L2 satisfy all of the relationships in the following formulas (1) to (4).

[0059] 1.0≦L / W≦2.0 Formula (1) 0.4≦L1 / L≦0.5 Formula (2) 0.4≦L2 / L≦0.5 Equation (3) 0.9≦L1 / L2≦1.1 Equation (4)

[0060] (5) Inner middle area 14C As shown in Figures 2, 3 and 6, the inner intermediate region 14C provided between the inner center main groove 12B and the inner shoulder main groove 12D includes a plurality of inner intermediate blocks 18C1, 18C2 arranged in the tire circumferential direction CD, and a plurality of inner intermediate slits 16C provided between the inner intermediate blocks 18C1, 18C2.

[0061] Specifically, the inner intermediate region 14C includes a plurality of first inner intermediate blocks 18C1 each having a first inner intermediate notch 40 and a plurality of second inner intermediate blocks 18C2 each having a second inner intermediate notch 41. The first inner intermediate blocks 18C1 and the second inner intermediate blocks 18C2 are alternately arranged in the tire circumferential direction CD.

[0062] The first inner intermediate notch 40 is a lateral groove-like notch with one end opening into the inner center main groove 12B and the other end terminating within the inner intermediate region 14C, and is inclined with respect to the tire axial direction AD so as to extend in a direction parallel to the second center slit 16A2 provided in the center rib 18A. The first inner intermediate notch 40 is provided such that at least a part of the opening opening into the inner center main groove 12B faces the opening of the second center slit 16A2 to the inner center main groove 12B in the extension direction of the second center slit 16A2.

[0063] The second inner intermediate notch 41 is a lateral groove-like notch whose one end in its extension direction opens into the inner shoulder main groove 12D and whose other end terminates within the inner intermediate region 14C, and is inclined with respect to the tire axial direction AD so as to extend in a direction parallel to the second center slit 16A2 and the first inner intermediate notch 40 provided in the center rib 18A.

[0064] The inner intermediate slits 16C provided in the inner intermediate region 14C are recessed grooves extending in a direction intersecting the tire circumferential direction CD so as to open into the inner center main groove 12B and the inner shoulder main groove 12D. The inner intermediate slits 16C are provided with a first slit bend portion 16C1 on the inner center main groove 12B side and a second slit bend portion 16C2 on the inner shoulder main groove 12D side at a distance from the first slit bend portion 16C1 to the tire axially outer side AWo. The inner intermediate slits 16C are bent from one side in the tire circumferential direction to the other side at the first slit bend portion 16C1 and bent from the other side in the tire circumferential direction to one side at the second slit bend portion 16C2.

[0065] As a result, the portion of the inner intermediate slit 16C from the inner center main groove 12B to the first slit bend portion 16C1 is inclined in the same direction as the second center slit 16A2 with respect to the tire axial direction AD, the portion from the first slit bend portion 16C1 to the second slit bend portion 16C2 is inclined in the opposite direction to the second center slit 16A2 with respect to the tire axial direction AD, and the portion from the second slit bend portion 16C2 to the inner shoulder main groove 12D is inclined in the same direction as the second center slit 16A2 with respect to the tire axial direction AD.

[0066] The first inner intermediate block 18C1 and the second inner intermediate block 18C2 are provided with a first inner intermediate sipe 42 and a second inner intermediate sipe 43, which extend in a direction intersecting the tire circumferential direction CD so that one end opens into the inner center main groove 12B and the other end opens into the inner shoulder main groove 12D. In this embodiment, the first inner intermediate sipe 42 and the second inner intermediate sipe 43 extend in the sipe length direction while repeatedly curving or bending as shown in Fig. 6 in a plan view, and the cross-sectional shape parallel to the tread surface forms a wave shape having an amplitude in the sipe width direction.

[0067] The amplitude center line of the first inner intermediate sipe 42 has a first bent portion 42A on the inner center main groove 12B side, and a second bent portion 42B on the inner shoulder main groove 12D side, spaced axially outward from the first bent portion 42A, and bent from one side in the tire circumferential direction to the other at the first bent portion 42A, and bent from the other side in the tire circumferential direction to one side at the second bent portion 42B.

[0068] The first inner intermediate sipe 42 is divided at the second bend portion 42B. That is, the first inner intermediate sipe 42 is composed of an inner sipe portion 42C extending from the inner center main groove 12B to the axially outer side AWo of the tire, and an outer sipe portion 42D extending from the inner shoulder main groove 12D to the axially inner side AWi of the tire. The inner sipe portion 42C and the outer sipe portion 42D are provided facing each other in the tire axial direction AD with a gap therebetween on the inner shoulder main groove 12D side from the tire axial center of the first inner intermediate block 18C1 such that their projections in the tire circumferential direction CD at least partially overlap each other.

[0069] The amplitude center line of the second inner intermediate sipe 43 has a first bent portion 43A on the inner center main groove 12B side, and a second bent portion 43B on the inner shoulder main groove 12D side, spaced axially outward from the first bent portion 43A, and bent from one side in the tire circumferential direction to the other at the first bent portion 43A, and bent from the other side in the tire circumferential direction to one side at the second bent portion 43B.

[0070] The second inner intermediate sipe 43 is divided at the first bend portion 43A. That is, the second inner intermediate sipe 43 is composed of an inner sipe portion 43C extending from the inner center main groove 12B to the tire axially outer side AWo, and an outer sipe portion 43D extending from the inner shoulder main groove 12D to the tire axially inner side AWi. The inner sipe portion 43C and the outer sipe portion 43D are provided facing each other in the tire axial direction AD with a gap in the tire axial direction AD on the inner center main groove 12B side from the tire axial center of the first inner intermediate block 18C1 so that their projections in the tire circumferential direction CD at least partially overlap each other.

[0071] Further, in the first inner intermediate block 18C1, a plurality of third inner intermediate sipes 44 extending in a direction intersecting the tire circumferential direction CD are provided at intervals in the tire circumferential direction CD on both sides in the tire circumferential direction CD of the first inner intermediate sipe 42. The third inner intermediate sipe 44 extends in the sipe length direction while repeatedly curving or bending as shown in Fig. 6 in a plan view, and its cross-sectional shape parallel to the tread surface forms a wave shape having amplitude in the sipe width direction, and the amplitude center line of the third inner intermediate sipe 44 extends in a direction parallel to the first inner intermediate sipe 42.

[0072] In the second inner intermediate block 18C2, a plurality of fourth inner intermediate sipes 45 extending in a direction intersecting the tire circumferential direction CD are provided at intervals in the tire circumferential direction CD on both sides in the tire circumferential direction CD of the second inner intermediate sipe 43. The fourth inner intermediate sipe 45 extends in the sipe length direction while repeatedly curving or bending as shown in Fig. 6 in a plan view, and its cross-sectional shape parallel to the tread surface forms a wave shape having amplitude in the sipe width direction, and the amplitude center line of the fourth inner intermediate sipe 45 extends in a direction parallel to the second inner intermediate sipe 43.

[0073] The groove width of the inner intermediate slit 16C is preferably 2.5 mm to 4.5 mm, and more preferably 2.5 mm to 4.2 mm. The groove depth of the inner intermediate slit 16C is preferably 7.0 mm to 8.5 mm, and more preferably 7.2 mm to 8.2 mm. The groove width of the first inner intermediate notch 40 and the second inner intermediate notch 41 is preferably 2.0 mm to 5.0 mm, and more preferably 2.6 mm to 4.5 mm. The groove depth of the first inner intermediate notch 40 and the second inner intermediate notch 41 is preferably 1.0 mm to 5.5 mm, and more preferably 1.3 mm to 5.2 mm. The groove width of the first inner intermediate sipe 42, the second inner intermediate sipe 43, the third inner intermediate sipe 44, and the fourth inner intermediate sipe 45 is preferably 0.15 mm to 1.0 mm, and more preferably 0.3 mm to 0.4 mm. The groove depth of the first inner intermediate sipe 42, the second inner intermediate sipe 43, the third inner intermediate sipe 44 and the fourth inner intermediate sipe 45 is preferably 4.0 mm to 7.0 mm, and more preferably 6.0 mm to 6.5 mm.

[0074] (6) Outer shoulder area 14D As shown in FIG. 2, the outer shoulder region 14D includes a plurality of outer shoulder blocks 18D arranged side by side in the tire circumferential direction CD, and a plurality of outer shoulder slits 16D provided between the outer shoulder blocks 18D.

[0075] The outer shoulder slits 16D are recessed grooves extending in a direction intersecting the tire circumferential direction CD so as to open to the outer shoulder main groove 12C and the ground contact edge Eo, and are provided alternately in the tire circumferential direction CD. The outer shoulder slits 16D are provided such that at least a part of the opening opening to the outer shoulder main groove 12C faces the openings of the first outer intermediate slit 16B1 and the second outer intermediate slit 16B2 to the outer shoulder main groove 12C in the tire axial direction AD.

[0076] The outer shoulder block 18D is provided with a plurality of (e.g., three) outer shoulder sipes 38 spaced apart in the tire circumferential direction CD. The outer shoulder sipes 38 extend in a direction intersecting the tire circumferential direction CD, with one end opening into the outer shoulder main groove 12C and the other end opening into the ground contact edge Eo. The outer shoulder sipes 38 extend in the length direction of the sipe while repeatedly curving or bending as shown in Fig. 2 in a plan view, and the cross-sectional shape parallel to the tread surface forms a wave shape having amplitude in the sipe width direction.

[0077] (7) Inner shoulder area 14E As shown in FIG. 2, the inner shoulder region 14E includes a plurality of inner shoulder blocks 18E arranged side by side in the tire circumferential direction CD, and a plurality of inner shoulder slits 16E provided between the inner shoulder blocks 18E.

[0078] The inner shoulder slits 16E are recessed grooves extending in a direction intersecting the tire circumferential direction CD so as to open to the inner shoulder main groove 12D and the ground contact edge Ei, and are provided alternately in the tire circumferential direction CD. The inner shoulder slits 16E are provided such that at least a part of the opening opening to the inner shoulder main groove 12D faces the opening of the inner intermediate slit 16C to the inner shoulder main groove 12D in the tire axial direction AD.

[0079] The inner shoulder block 18E is provided with a plurality of (e.g., three) inner shoulder sipes 39 spaced apart in the tire circumferential direction CD. The inner shoulder sipes 39 extend in a direction intersecting the tire circumferential direction CD, with one end opening into the inner shoulder main groove 12D and the other end opening into the ground contact edge Ei. The inner shoulder sipes 39 extend in the length direction of the sipe while repeatedly curving or bending as shown in FIG. 2 in a plan view, and the cross-sectional shape parallel to the tread surface is a wave shape having an amplitude in the sipe width direction. In this embodiment, the inner shoulder sipes 39 are formed of sawtooth-shaped sipes with a longer period of repetition of curvature or bending compared to the outer shoulder sipes 38.

[0080] (8) Effects In the pneumatic tire 1 of this embodiment, the outer center main groove 12A, which is located on the vehicle outer side of the tire equatorial plane, has a narrower groove width and a shallower groove depth than the inner center main groove 12B, the outer shoulder main groove 12C, and the inner shoulder main groove 12D. This makes it possible to suppress a decrease in tread rigidity in the axial center portion of the pneumatic tire 1 near the vehicle outer side, thereby ensuring steering stability.

[0081] In the pneumatic tire 1 of this embodiment, a center slit 16A1 opening into the outer center main groove 12A and a center slit 16A2 opening into the inner center main groove 12B are alternately provided in the tire circumferential direction CD on the extension of the outer intermediate slits 16B1, 16B2 in the center region 14A. This ensures the rigidity of the center region 14A while providing a high edge effect due to the center slits 16A1, 16A2, thereby achieving both steering stability and driving performance on snowy and icy roads.

[0082] In the pneumatic tire 1 of this embodiment, a first outer intermediate sipe 35 and a second outer intermediate sipe 36 are provided in the central portion of the outer intermediate block 18B in the tire circumferential direction CD, so that a high edge effect can be obtained by the sipes 35, 36, and the central portion of the outer intermediate block 18B in the tire circumferential direction CD is not divided by the sipes, so block rigidity can be ensured, and it is possible to achieve both steering stability and driving performance on icy and snowy roads.

[0083] In the pneumatic tire 1 of this embodiment, the third outer intermediate sipe 37 penetrating the outer intermediate block 18B in the tire axial direction AD is provided, so that a high edge effect is obtained. Moreover, the third outer intermediate sipe 37 is provided on the outer intermediate block 18B outside in the tire circumferential direction than the first outer intermediate sipe 35 and the second outer intermediate sipe 36, so that a decrease in rigidity of the outer intermediate block 18B can be suppressed.

[0084] When the pneumatic tire 1 of this embodiment has the above lengths W, L, L1, and L2 that satisfy all of the relationships of the above formulas (1) to (4), the shape of the contact surface of the land portion sandwiched between the outer shoulder main groove 12C and the inner center main groove 12B in the tire axial direction AD and between adjacent first outer intermediate slits 16B1 in the tire circumferential direction CD will not be elongated in either the tire circumferential direction CD or the tire axial direction AD, but will be close to a substantially square shape, so that even if a slit is provided, a decrease in the rigidity of the land portion can be suppressed.

[0085] That is, in this embodiment, the outer center main groove 12A is narrower in width and shallower in depth than the other main grooves 12B, 12C, and 12D, and the second center slit 16A2 is not connected to the second outer intermediate slit 16B2. Therefore, the land portion sandwiched between the outer shoulder main groove 12C and the inner center main groove 12B in the tire axial direction AD and between the adjacent first outer intermediate slits 16B1 in the tire circumferential direction CD functions as a single land portion in a pseudo manner. When the length L is close to the length W (when L / W is close to 1), this land portion becomes a shape close to a square, and the land portion rigidity is less likely to decrease. Also, when the length L is greater than the length W and L / W is close to 2, the outer intermediate block 18B becomes a shape close to a square, and the land portion rigidity is less likely to decrease.

[0086] In this embodiment, the belt reinforcing layer 9 is provided in the shoulder regions 14D and 14E, and the center region 14A is not provided with the belt reinforcing layer, so that the tire can easily contact the ground near the tire equatorial plane CL, and the steering stability can be improved. In addition, in this embodiment, the inclination angle of the belt cords constituting the belt plies 7A and 7B of the belt layer 7 with respect to the tire circumferential direction is set to 23 degrees or more and 29 degrees or less, so that the steering stability can be improved.

[0087] In this embodiment, in the inner intermediate region 14C, a first inner intermediate block 18C1 provided with a first inner intermediate notch 40 opening to the inner center main groove 12B and a second inner intermediate block 18C2 provided with a second inner intermediate notch 41 opening to the inner shoulder main groove 12D are alternately provided in the tire circumferential direction. As a result, the notches 40, 41 are evenly arranged on both sides of the tire axial direction AD in the inner intermediate region 14C, so that the edge effect of the notches 40, 41 can be obtained while the block rigidity is uniformed and the ground contact pressure can be distributed.

[0088] The inner intermediate blocks 18C1, 18C2 are provided with wavy inner intermediate sipes 42, 43 extending in a direction intersecting the tire circumferential direction CD so that one end opens into the inner center main groove 12B and the other end opens into the inner shoulder main groove 12D, and since the inner intermediate sipes 42, 43 are divided at the bend portions 42B, 43A, the edge effect can be improved while suppressing the reduction in rigidity of the inner intermediate blocks 18C1, 18C2 due to the inner intermediate sipes 42, 43.

[0089] In the first inner intermediate block 18C1, the inner intermediate notch 40 is provided on the inner center main groove 12B side, and the bent portion 42B where the sipe 42 is divided is provided on the inner shoulder main groove 12D side, while in the second inner intermediate block 18C2, the inner intermediate notch 41 is provided on the inner shoulder main groove 12D side, and the bent portion 43A where the sipe 43 is divided is provided on the inner center main groove 12B side. This makes it possible to improve the edge effect while suppressing a decrease in rigidity of the inner intermediate blocks 18C1, 18C2 due to the inner intermediate notches 40, 41 and the inner intermediate sipes 42, 43.

[0090] In this embodiment, the outer center main groove 12A is narrower and shallower than the inner center main groove 12B, but the first center slit 16A1 connected to the outer center main groove 12A is deeper than the second center slit 16A2 connected to the inner center main groove 12B. This makes it possible to equalize the rigidity of the center region 14A on the outer side and the inner side of the vehicle, and ensures drainage on the outer side of the center region 14A.

[0091] (9) Example of changes Next, modified examples will be described. Various modifications can be made to the above embodiment without departing from the spirit of the invention. Modified examples will be described below. In addition to the following modified examples, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention.

[0092] In the above embodiment, the belt reinforcement layer 9 is provided in the shoulder regions 14D and 14E, but not in the center region 14A and the intermediate regions 14B and 14C. However, the belt reinforcement layer 9 may be provided in the center region 14A, the intermediate regions 14B and 14C, and the shoulder regions 14D and 14E so as to cover the entire belt layer 7. When the belt reinforcement layer 9 is provided so as to cover the entire belt layer 7, it is preferable that the belt reinforcement layer 9 provided in the center region 14A is thinner than the belt reinforcement layer 9 provided in the shoulder regions 14D and 14E. By providing the belt reinforcement layer 9 in the center region 14A to be thinner than the shoulder regions 14D and 14E, the tire can easily contact the ground near the tire equatorial plane CL, and the steering stability can be improved. [Explanation of symbols]

[0093] 1...pneumatic tire, 3...tread, 4...sidewall, 5...carcass layer, 7...belt layer, 8...tread rubber, 9...belt reinforcing layer, 12A...outer center main groove, 12B...inner center main groove, 12C...outer shoulder main groove, 12D...inner shoulder main groove, 14A...center region, 14B...outer intermediate region, 14C...inner intermediate region, 14D...outer shoulder region, 14E...inner shoulder region, 16A1...first center slit, 16A2...second center slit, 16B1...first outer intermediate slit, 16B1a...bending portion, 16B2...second outer intermediate slit, 16B2a...bending portion, 16C...inner intermediate slit, 16C1...first slit bend portion, 16C2...second slit bend portion, 18A...center rib, 18B ...second outer intermediate block, 18C1...first inner intermediate block, 18C2...second inner intermediate block, 18D...outer shoulder block, 18E...inner shoulder block, 30...compound sipe, 33...first outer intermediate notch, 34...second outer intermediate notch, 35...first outer intermediate sipe, 35a...bend portion, 36...second outer intermediate sipe, 36a...bend portion, 37...third outer intermediate sipe, 37a...bend portion, 38...outer shoulder sipe, 39...inner shoulder sipe, 40...first inner intermediate notch, 41...second inner intermediate notch, 42...first inner intermediate sipe, 42A...first bend portion, 42B...second bend portion, 42C...inner sipe portion, 42D...outer sipe portion, 43...second inner intermediate sipe, 43A...first bend portion, 43B...second bend portion

Claims

1. A pneumatic tire having a tread in which three or more main grooves extending in the tire circumferential direction are formed in the tread rubber, and the mounting direction on a vehicle is specified, The tread rubber of the pneumatic tire includes an outer center main groove provided on the vehicle outer side of the tire equatorial plane, an inner center main groove provided on the vehicle inner side of the tire equatorial plane, an inner shoulder main groove adjacent to the inner center main groove on the tire axially outer side, and an inner middle region defined by the inner center main groove and the inner shoulder main groove, The inner intermediate region includes a plurality of inner intermediate blocks arranged in a tire circumferential direction and a plurality of inner intermediate slits provided between the inner intermediate blocks, the plurality of inner intermediate blocks include a first inner intermediate block having a first inner intermediate notch that opens into the inner center main groove and a second inner intermediate block having a second inner intermediate notch that opens into the inner shoulder main groove, The first inner intermediate blocks and the second inner intermediate blocks are provided alternately in a tire circumferential direction.

2. the first inner intermediate block and the second inner intermediate block each include a wave-shaped inner intermediate sipe extending in a direction intersecting the tire circumferential direction so that one end opens into the inner center main groove and the other end opens into the inner shoulder main groove, The amplitude center line of the inner intermediate sipe is bent in opposite directions to each other at a first bend portion provided on the axially inner side of the inner intermediate block and at a second bend portion provided on the axially outer side of the inner intermediate block, The pneumatic tire according to claim 1 , wherein the inner intermediate sipe is interrupted at one of the first bend portion and the second bend portion.

3. 3. The pneumatic tire according to claim 2, wherein the inner intermediate sipe provided in the first inner intermediate block is separated at the second bend portion, and the inner intermediate sipe provided in the second inner intermediate block is separated at the first bend portion.

4. The pneumatic tire according to claim 1 , wherein the inner intermediate slit includes a first slit bend portion bent from one side in the tire circumferential direction to the other side, and a second slit bend portion bent from the other side in the tire circumferential direction to one side.

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